Luk 8:16 “No one lights a lamp and then covers it with a jar or puts it under a bed, but puts it on a lampstand so that those who come in can see the light.
Luk 8:17 Because nothing is hidden that will not be revealed, and nothing concealed that will not be made known and brought to light.
Luk 8:18 So listen carefully, because whoever has will be given more, but whoever does not have, even what he thinks he has will be taken away from him.”

invisible Christianity

Jesus has just given an illustration about different soils reacting to the seed differently, but only one soil producing a lasting crop. Now, Jesus continues to preach on the same topic, but changes the illustration. He now uses the illustration of lighting a lamp, exposing reality by bringing it to light. Relating this message to the last one, it is clear that some of the soils appear to be producing fruit (the rocky and rootless, which fall away after a time of testing; the thorny, which are choked by the worries and desires, not living to maturity).

So, the message that Jesus is illustrating is this: invisible Christianity is not genuine Christianity. Real Christianity is made known — brought to the light. But those who only think they have it will be shown to not have it at all.